• Journal of Biosystems Engineering
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• 제36권5호
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• pp.355-360
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• 2011

This study was carried out to analyze the installation effect of an anti-wind net on reducing wind velocity which was used to protect orchards as well as single-span plastichouses. The pressure drop through three types of anti-wind net was measured in a subsonic wind tunnel. The wind reduction through the anti-wind facility for several sets in respect to three types of the net and heights of the facility ranging from 3 to 11 m was analyzed by using computational fluid dynamics (CFD). The measured data showed that the pressure drop increased as an equation of the second degree of the inlet wind velocity. Numerical computations exhibited that the effect of wind reduction definitely augmented as the net size became smaller and increased with the height of the facility being heightened to some extent. For the typical and widely used anti-wind facility with a height of 5 m and a net size of 4mm, the amount of wind reduction came up to 5.1 m/s for the inlet wind velocity of 20 m/s, and also 7.6 and 10.1 m/s for the inlet wind velocities of 30 and 40 m/s, respectively. In case for the orchard's longitudinal length to be within about 200 m, the appropriately effective height of the facility was predicted to be 5 m. Finally, the negative total pressure on the top face of the single-span plastichouse certainly reduced for all the cases with the anti-wind facility being installed. In particular, the reduction of the negative total pressure was more considerable as the inlet wind velocity increased.

• 한국음향학회지
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• 제38권3호
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• pp.352-362
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• 2019

가로변 이면지역에 위치한 노후된 공동주택은 주도로의 교통소음의 피해를 받는다. 이면지역의 소음은 가로면 건물의 높이와 주도로와의 이격거리, 그리고 도로변 건물간의 이격거리 및 도로변 건물간의 높이차이에 의하여 영향을 받는다. 본 연구는 한 도시 내의 15개의 블록을 선정하여 가로변 건물배치형태를 1)블록에 단일건물이 배치된형태, 2)블록에 다수의 건물이 하나의 축으로 연속하여 배치된 형태로 분류하였으며, 가로변과 이면지역에서 도로교통소음을 동시에 측정하여 가로변의 건물 배치형식에 따른 이면지역소음의 상관성을 분석하였다. 분석결과, 이면지역으로 전달된 도로교통소음은 가로변에 배치된 건물의 높이, 건물과 건물간의 이격된 거리, 인접한 건물의 높이차에 영향을 받으며 건물의 너비에 의한 소음도의 감소는 나타나지 않았다. 가로변에 위치한 건물의 높이가 4 m(단층)인 경우 이면지역의 소음도는 12 dB(A)감소하였으며 높이가 4 m 증가할 때마다 2 dB(A)씩 감소하는 것으로 나타났다. 또한 인접한 두 건물의 높이차가 4 m 증가할 때마다 이면지역의 소음도는 1 dB(A)씩 증가하였으며, 인접한 두 건물의 이격된 거리가 0.5 m 증가할 때마다 이면지역의 소음도는 1 dB(A)씩 증가하는 것으로 나타났다.

• KSTLE International Journal
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• 제3권2호
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• pp.114-118
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• 2002

In this work, head-disk interactions are studied when flying height becomes lower than laser bump height on the landing zone of a disk. With the reduction of the spinning speed in a spin stand, the flying height is decreased under the height of laser bumps. Conventional and padded pico sliders sweep between landing Bone and data zone and, then, the dynamic behavior of the pico sliders and head-disk impacts are investigated using AE and stiction/friction signals. After 200n cycle-sweep tests, bearing analysis and AFM analysis indicate that there are some signs of wear and plastic deformation in the landing zone of a disk, although AE and stiction/friction signals are not significantly changed during the sweep tests. The experimental results of this paper suggest that in CSS tests at component level, more rigorous examination methods of wear and plastic deformation might be necessary as flying height becomes getting lower.

• Journal of Periodontal and Implant Science
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• 제40권2호
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• pp.69-75
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• 2010

Purpose: Implant survival rates using a bone-added osteotome sinus floor elevation (BAOSFE) procedure with simultaneous placement of a non-submerged sand blasted with large grit and acid etched (SLA) implant are well documented at sites where native bone height is less than 5 mm. This study evaluated the clinical results of non-submerged SLA Straumann implants placed at the time of the BAOSFE procedure at sites where native bone height was less than 4 mm. Changes in graft height after the BAOSFE procedure were also assessed using radiographs for 5 years after the implant procedure. Methods: The BAOSFE procedure was performed on 4 patients with atrophic posterior maxillas with simultaneous placement of 7 non-submerged SLA implants. At least 7 standardized radiographs were obtained from each patient as follows: before surgery, immediately after implant placement, 6 months after surgery, every year for the next 3 years, and after more than 5 years had passed. Clinical and radiographic examinations were performed at every visit. Radiographic changes in graft height were calculated with respect to the implant's known length and the original sinus height. Results : All implants were stable functionally, as well as clinically and radiographically, during the follow-up. Most of the radiographic reduction in the grafted bone height occurred in the first 2 years; reduction after 2 years was slight. Conclusions: The simultaneous placement of non-submerged SLA implants using the BAOSFE procedure is a feasible treatment option for patients with severe atrophic posterior maxillas. However, the grafted bone height is reduced during the healing period, and patients must be selected with care.

• Steel and Composite Structures
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• 제23권4호
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• pp.409-420
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• 2017

This paper theoretically studies the cyclic behavior of hybrid connections between steel coupling beams and concrete shear walls with embedded steel columns. Finite element models of connections with long and short embedded steel columns are built in ABAQUS and validated against the test results in the companion paper. Parametric studies are carried out using the validated FE model to determine the key influencing factors on the load-bearing capacity of connections. A close-form solution of the load-bearing capacity of connections is proposed by considering the contributions from the compressive strength of concrete at the interface between the embedded beam and concrete, shear yielding of column web in the tensile region, and shear capacity of column web and concrete in joint zone. The results show that the bond slip between embedded steel members and concrete should be considered which can be simulated by defining contact boundary conditions. It is found that the loadbearing capacity of connections strongly depends on the section height, flange width and web thickness of the embedded column. The accuracy of the proposed calculation method is validated against test results and also verified against FE results (with differences within 10%). It is recommended that embedded steel columns should be placed along the entire height of shear walls to facilitate construction and enhance the ductility. The thickness and section height of embedded columns should be increased to enhance the load-bearing capacity of connections. The stirrups in the joint zone should be strengthened and embedded columns with very small section height should be avoided.

• 대한방사선기술학회지:방사선기술과학
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• 제45권4호
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• pp.313-320
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• 2022

Both angiography and interventional procedures accompanied by angiography provide many diagnostic and therapeutic benefits to patients and are rapidly increasing. However, unlike general radiography or computed tomography using the same X-ray, the amount of radiation is quite high, but the dose range can vary considerably for each patient and operator. The high sensitivity of the lens to radiation during cerebral angiography and neurointervention is already well known, and although there are many related studies, it is insufficient to easily reduce radiation in diagnosis and treatment. In this situation, in particular, by adding three-dimensional rotational angiography (3D-RA) to the existing two-dimensional (2D) angiography, it is now possible to make an accurate diagnosis. However, since this 3D-RA acquires images through projection of more radiation than before, the exposure dose of the lens may be higher. Therefore, we tried to analyze whether the radiation dose of the lens can be reduced by moving the lens out of the field range by adjusting the table height and magnification ratio during the examination using 3D-RA. The surface dose was measured using a rando phantom and a radiophotoluminescent glass dosimeter (PLD) and the radiation dose was compared by adjusting the table height and magnification ratio based on the central point. As a result, it was found that the radiation dose of the lens decreased as the table height increased from the central point, that is, as the lens was out of the field of view. In conclusion, in 3D-RA, moving the table position of about 2 cm in height will make a significant contribution to the dose reduction of the lens, and it was confirmed that adjusting the magnification ratio can also reduce the surface dose of the lens.

• Journal of Periodontal and Implant Science
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• 제36권2호
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• pp.345-359
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• 2006

Loss of maxillary molar teeth leads to rapid loss of crestal bone and inferior expansion of the maxillary sinus floor (secondary pneumatization). Rehabilitation of the site with osseointegrated dental implants often represents a clinical challenge because of the insufficient bone volume resulted from this phenomenon. Boyne & James proposed the classic procedure for maxillary sinus floor elevation entails preparation of a trap door including the Schneiderian membrane in the lateral sinus wall. Summers proposed another non-invasive method using a set of osteotome and the osteotome sinus floor elevation (OSFE) was proposed for implant sites with at least 5-6mm of bone between the alveolar crest and the maxillary sinus floor. The change of grafted material in maxillary sinus is important for implant survival and the evaluation of graft height after maxillary sinus floor elevation is composed of histologic evaluation and radiomorphometric evaluation. The aim of the present study was radiographically evaluate the graft height change after maxillary sinus floor elevation and the influence of the graft material type in height change and the bone remodeling of grafts in sinus. A total of 59 patients (28 in lateral approach and 31 in crestal approach) who underwent maxillary sinus floor elevation composed of lateral approach and crestal approach were radiographically followed for up to about 48 months. Change in sinusgraft height were calculated with respect to implant length (IL) and grafted sinus height(BL). It was evaluated the change of the graft height according to time, the influence of the approach technique (staged approach and simultaneous approach) in lateral approach to change of the graft height, and the influence of the type of graft materials to change of the graft height. Patients were divided into three class based on the height of the grafted sinus floor relative to the implant apex and evaluated the proportion change of that class (Class I, in which the grafted sinus floor was above the implant apex; Class II, in which the implant apex was level with the grafted sinus floor; and Class III, in which the grafted sinus floor was below the implant apex). And it was evaluated th bone remodeling in sinus during 12 months using SGRl(by $Br\ddot{a}gger$ et al). The result was like that; Sinus graft height decreased significantly in both lateral approach and crestal approach in first 12 months (p$MBCP^{TM}$ had minimum height loss. Class III and Class II was increased by time in both lateral and crestal approach and Class I was decreased by time. SGRI was increased statistically significantly from baseline to 3 months and 3 months(p<0.05) to 12 months(p$ICB^{(R)}$ single use, more reduction of sinusgraft height was appeared. Therefore we speculated that the mixture of graft materials is preferable as a reduction of graft materials. Increasing of the SGRI as time goes by explains the stability of implant, but additional histologic or computed tomographic study will be needed for accurate conclusion. From the radiographic evaluation, we come to know that placement of dental implant with sinus floor elevation is an effective procedure in atrophic maxillary reconstruction.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 춘계학술대회 논문집
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• pp.175-182
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• 1994

Effect of some process variables including area reduction, stroke advance, materials on the extrusion load, plastic flow and height ratio of upper to lower extruded parts in the cup-cup axisymmetric extrusion were experimentally investigated and analyzed. Deformed pattern is visualized by grid-marking technique using half-cut billets splitted. The influence of using split specimen and original specimen on the extrusion load and height ratio is examined by experiment.

• Structural Engineering and Mechanics
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• 제62권2호
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• pp.209-224
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• 2017

Elevated water tanks are considered as important structures due to its post-earthquake requirements. Elevated water tank on reinforced concrete frame staging is widely used in India. Different response reduction factors depending on ductility of frame members are used in seismic design of frame staging. The study on appropriateness of response reduction factor for reinforced concrete tank staging is sparse in literature. In the present paper a systematic study on estimation of key components of response reduction factors is presented. By considering the various combinations of tank capacity, height of staging, seismic design level and design response reduction factors, forty-eight analytical models are developed and designed using relevant Indian codes. The minimum specified design cross section of column as per Indian code is found to be sufficient to accommodate the design steel. The strength factor and ductility factor are estimated using results of nonlinear static pushover analysis. It was observed that for seismic design category 'high' the strength factor has lesser contribution than ductility factor, whereas, opposite trend is observed for seismic design category 'low'. Further, the effects of staging height and tank capacity on strength and ductility factors for two different seismic design categories are studied. For both seismic design categories, the response reduction factors obtained from the nonlinear static analysis is higher than the code specified response reduction factors. The minimum dimension restriction of column is observed as key parameter in achieving the desired performance of the elevated water tank on frame staging.

• 한국농공학회논문집
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• 제53권4호
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• pp.49-57
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• 2011

The objective of this study was to experimentally investigate the feasibility of SRI (system of rice intensification) in Korean rice farming. Eight experimental plots of $5{\times}15$ m in size were prepared on an existing rice field of loam soil. Spacing was $30{\times}15$ cm (conventional treatment: CT), $30{\times}30$ cm, $40{\times}40$ cm and $50{\times}50$ cm, respectively. CT were flooded and SRI plots irrigated intermittently 3 to 5 day interval during cultivation. Organic matter content and pH of the soil were $2.5{\pm}0.03$ % and $6.1{\times}0.2$, respectively, before the cultivation. The highest number of tillers and height of the plant were measured at $50{\times}50$ cm plots. The height and number of tillers and height in $50{\times}50$ cm plots were 10 cm and 1.5 times more than CT. Average irrigation supply to SRI and CT was 243.2 mm and 547.3 mm, respectively. It meant that the reduction of irrigation water in SRI plots over CT was estimated to 55.6 %. Therefore SRI was concluded to have a good enough possibility to be applied in South Korea because it was proven to be more effective in reduction of irrigation water and crop cultivation compare to the CT.